This invention relates to repair of an ultrasonic rotary horn.
Ultrasonic rotary horns are used to distribute ultrasonic energy in a variety of industrial processes. One example involves bonding of two thermoplastic sheets of material together in the manufacture of personal care products such as diapers. Other examples involve perforating; and other examples involve shape cutting.
An ultrasonic rotary horn may, for example, be manufactured from a titanium-based material such as commercially pure titanium or a titanium alloy (e.g., Ti6Al4V). In other apparatus it may be manufactured from, for example, aluminum-based materials, monel, or some alloy steels. An ultrasonic rotary horn may in certain circumstances work in conjunction with a hard or aggressive anvil, such as a metal anvil, with a work piece between a radial energy transfer surface of the horn and the anvil. Over time, contact between the energy transfer surface and the anvil and/or between the energy transfer surface and the work piece can cause abrasive wear and deformation on the radial energy transfer surface of the horn. These deteriorated conditions can detract from the efficiency of energy transfer to work piece, and can cause imperfect bonding, perforating, shape cutting, or other work being performed on the work piece.
Periodically, wear on the radial energy transfer surface must be addressed by machining worn metal from the radial energy transfer surface. After one or more such machining operations, the horn diameter has been reduced by metal removal to a point where the diameter is below minimum specifications, and the horn must be scrapped. As the horn diameter is reduced, the resonant frequency rises to a value which is too high.
In response to the above difficulties and problems, the invention provides for repair of ultrasonic rotary horns to restore the radial energy transfer surface without significantly reducing the horn diameter, thereby reducing the frequency with which horns must be scrapped.
Briefly, therefore, the invention is directed to a method for repairing a radial energy transfer surface of an ultrasonic rotary horn comprising a shaped metal horn body and the radial energy transfer surface with a deteriorated metal condition thereon. A radial depth of metal having a deteriorated metal condition is removed from the radial surface of the horn to yield a reduced-diameter ultrasonic rotary horn having a radial surface free from the deteriorated metal condition. A metal powder is applied to the radial surface free from the deteriorated metal condition to yield an ultrasonic rotary horn having a radial surface free from deteriorated metal condition and with metal powder thereon. The ultrasonic rotary horn having the radial surface free from deteriorated metal condition and with metal powder thereon is hot isostatically pressed to consolidate the metal powder and fuse the metal powder to the radial surface to yield a repaired radial energy transfer surface comprising consolidated metal fused to the radial surface free from the deteriorated metal condition.
The invention is also directed to a repaired ultrasonic rotary horn having a shaped metal horn body, and a radial energy transfer surface comprising consolidated metal powder fused to a radial surface of the shaped metal horn body by hot isostatic pressing such that the consolidated metal powder has a density of at least about 95% of a theoretical density of the consolidated metal powder.
Other features and advantages will be in part apparent and in part pointed out hereinafter.